The present invention relates to a sickleless internal gear pump with sealing elements fitted in the tooth heads and actuated by pressure ducts positioned behind the sealing elements.
Such a pump includes an internally toothed ring gear and a pinion that meshes with the ring gear, the two gears being rotatably received in a common casing wherein the axial width of the casing matches the width of the ring gear and pinion. The casing includes a suction port and a pressure port, and the ring gear includes radial conduits to permit ingress and egress of the fluid medium being pumped. Either of the ring gear or pinion includes a sealing element radially moveable in a profile groove in the tooth head, the sealing element sliding on the opposed tooth head of the other of the pinion or ring gear. The sealing elements include control spaces wherein pressure is applied from the rear.
A pump of this type is disclosed in DE 41 40 293 A1 which is based on DE 41 04 397 A1. U.S. patent application Ser. No. 08/163,033 relates to optimizing the pressure buildup between the opposed tooth heads of the ring gear and pinion wherein there is a rear application of pressure on the sealing elements. This is accomplished by providing in the sealing element a plurality of holes or a lateral groove by way of which part of the working pressure is allowed to act on the sealing element.
This hydraulic relief of the sealing element taught by application Ser. No. 08/163,033 has conceptually, and in practice, the disadvantages that each individual sealing element must include the holes or grooves. The control holes or grooves require mechanical machining which entails relatively high production costs.
The problem underlying the present invention is to provide a simpler, and thus more cost-effective, solution to the rear application of pressure on the radial sealing elements.